12/29/2023 0 Comments Super contra game over sound![]() checking to see which pin is tied to +5V makes it super easy to identify which type of chip is expected here. You can find the differing pinouts here, and as you can see from the pinouts the easiest way to tell them apart is the Vcc Pin. The other is an “MROM” format used by 27c400 and 27c4100. There is the JEDEC format which is used by 27c4096 and 27c4002, however this format is 16-bit only so that’s not likely it since it’s not going to work for our 8-bit k007232 audio ROM. There are at least 2 different common pin configurations for 4mbit DIP40 EPROMs. The idea if being able to shrink the PCB stack to half it’s current size AND potentially fix my PCB in the process seems like a lot more fun than trying to work out what component on the expansion board is bad So I start de-soldering the unpopulated locations in preparation for sockets. It looks to me like the expansion board can be completely eliminated by installing some sockets in these locations, and then merging the data from the 36 ROMs into just 5 4mbit ROMs. and each one of those chips has 2 16-bit 4mbit unpopulated location between the chips and an expansion board connector (see photos below). Similarly, the sprite (k051960) and title (k052109) data happen to have 8mbit of 32-bit data each. Looking at this I see that the section labeled “k007232” is 4mbit in size, and is 8-bit data and between the k007232 IC and one of the expansion board connectors there just so happens to be an empty 8-bit 4mbit EPROM location (see photo above). ![]() ROM_REGION( 0x10000, "audiocpu", 0 ) /* 64k for the SOUND CPU */ ROM_REGION( 0x20000, "maincpu", 0 ) /* banked program ROMs */ Looking at the MAME driver I see that the 5 unpopulated 4mbit sockets are exactly the same size as all 36 chips on the expansion board. I start looking over the board again for clues when I notice that each of the 3 expansion board connectors on the main board also has some large, unpopulated, ROM sockets. Most likely there is more than one resistor network that needs replace or maybe a bad logic IC. So apparently half the ROMs on the expansion board are “BAD” doubtful. Normally at this point I’d do simple check like dump the ROMs and verify their content against MAME unfortunately there 36 ROMs on this expansion board and all of them are soldered in place! I decide to look up if there is a dip switch for test mode and hope that there is a ROM check. So I replace that and check again… no change □ I notice that one of the Resistor Arrays on the expansion board is badly damaged, that seems to be the only obvious problem I can find beyond the board being pretty dusty. the Super Contra PCB is a 2-Board set with the main board on top and an equally sized ROM expansion board attached below for the graphics and audio ROMs. OK, so first thing is first, lets just see if there is any obvious physical damage.
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